Add view controller finding functions

We need them to be able to present another view controller

RCTVideo.m

@@ -524,6 +524,26 @@ static NSString *const playbackBufferEmptyKeyPath = @"playbackBufferEmpty";
   }
 }
 
+#pragma mark - View Controller retrieval
+
+// http://stackoverflow.com/questions/1340434/get-to-uiviewcontroller-from-uiview/2596519
+
+- (UIViewController *) firstAvailableUIViewController {
+    // convenience function for casting and to "mask" the recursive function
+    return (UIViewController *)[self traverseResponderChainForUIViewController];
+}
+
+- (id) traverseResponderChainForUIViewController {
+    id nextResponder = [self nextResponder];
+    if ([nextResponder isKindOfClass:[UIViewController class]]) {
+        return nextResponder;
+    } else if ([nextResponder isKindOfClass:[UIView class]]) {
+        return [nextResponder traverseResponderChainForUIViewController];
+    } else {
+        return nil;
+    }
+}
+
 #pragma mark - Lifecycle
 
 - (void)removeFromSuperview